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Mic Power Consumption

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Been looking at some short shotgun mics. I noticed that the operating power consumption varies a lot. For instance, the DPA 4017b uses 4.5mA, the 4017c consumes 2.8mA, while the Neumann KMR 81i sips a mere 0.8mA.

 

This leads me to wonder why some mics would be more more power hungry than others. I'm also curious to know whether this difference is significant enough to have a meaningful impact on the battery life of pre-amps, recorders, and... cameras.

 

I'm looking for a mic that will be used in relatively humid conditions and will live on-camera when not being used on a boom.

 

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9 minutes ago, mikewest said:

Why are you worried about power consumption???

 

mike

"battery life", extended time away from AC, and... curiosity?

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the math is quite straight forward: P = U * I

so the DPA draws 0.22W and the Neumann 0.04W on paper

 

compare that with the typical batteries you want to use and you get a rough estimate.

ie a single AA with about 2Wh runs the DPA for 10h and a 40Wh camera  battery for 200h, and five times that on the Neumann.

 

so for most people the power draw is negligible compared to the rest of the gear they run (recorder, wireless etc) and the other factors are far more important on choosing a mic (like how they sound and handle)

bests

chris

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If you look at the field of mics, and choose only shotguns with RF biasing, you get Sennheiser and the Rode NTG-3. I don't have a milliamperage figure for the NTG-3 at the moment but have reached out to someone who should know. (New info from Rode: It requires full spec phantom power and at least 5mA.) Rode very wisely chose to use the RF biasing to decrease humidity problems.

That begs the question of humidity problems. With my CMC641, which I have now owned for over 15 years, I have only had two incidents of humidity problem noise. That's back when I was overly scrupulous. I would dis-assemble the capsule and body after use and store them separately. I cleaned the contacts and stopped doing that and my humidity problems never happened again. My thought is that perhaps exposing the circular gold contacts allows air and schmutz to collect and that creates the noise. If you've never cleaned those contacts, perhaps you should. Be careful! Don't apply liquid cleaner in such a was as to allow it to drip down inside the power supply or capsule. Hold those parts with the contacts aimed DOWN and clean them (gently) from beneath. 

Most of my work has been done in the Mid-Atlantic US. In Summer, it can be EXCEPTIONALLY humid here for days at a time. I don't have data on Amazonian Rain Forests, but sometimes the air is so thick here that you can't see the top of a 1200' broadcast TV tower. 

Finally, one mic will probably create few problems other than shorter battery life, however, I have heard of situations in which multiple amperage-hungry mics could not run on a mixer or console because its amperage rating of the mixer/console Phantom Power supply was not sufficient to feed multiple "hungry" mics. 

 

Regards,

 

Ty Ford

Edited by Ty Ford
more info

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9 hours ago, chrismedr said:

 

so for most people the power draw is negligible compared to the rest of the gear they run (recorder, wireless etc) and the other factors are far more important on choosing a mic (like how they sound and handle)

bests

chris

+1

 

I’ve never actually noticed that different microphones cause different battery life when I’m using them. 

 

-Mike

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19 hours ago, MartinTheMixer said:

Hello, 

And then there's the Schoeps 2U at a whopping 170ma.

 

7.7 times the power used of the DPA.

 

Thanks, Martin

 

And. perhaps more significantly, the digital version of the above monetized Neumann KMR81i draws 150mA. 

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59 minutes ago, Constantin said:

 

And. perhaps more significantly, the digital version of the above monetized Neumann KMR81i draws 150mA. 

Constantin, "more significantly" because of? I want to make sure I'm not missing something here.

 

Also, that Neumann mic must have some serious downside, no one seems too excited about that one.

 

Sincerely, Martin

 

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1 hour ago, MartinTheMixer said:

Constantin, "more significantly" because of? I want to make sure I'm not missing something here.

 

Also, that Neumann mic must have some serious downside, no one seems too excited about that one.

 

Sincerely, Martin

 

 

No, there‘s nothing you missed. I was merely pointing to the Neumann D, because the comparison between its analog and its digital versions highlight even more the differences in power consumption between the two mics. Also, the OP mentioned the regular 81, so I thought this was information (kind of) pertinent to this thread. 

 

A lot of people use and love both versions of the KMR81i, but as I recently found out, the analog version has got no AM rf shielding, so it doesn’t work with digital transmitters. 

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On 3/7/2018 at 2:30 PM, Constantin said:

...KMR81i, but as I recently found out, the analog version has got no AM rf shielding, so it doesn’t work with digital transmitters. 

 

Good to know, I wasn't aware of that. Thanks.

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As John B. said, the DC converter circuitry in modern microphones is part of this. First-generation phantom powered microphones generally took the incoming 48 Volts and routed that through a high-value resistor to polarize the capsule. Those mikes generally had a single FET as their only active device, with an output transformer--miniaturized so as to fit into a 20 or 21 mm-diameter housing--that brought the output impedance down into the standard 150 or 200 Ohm range.

 

Transformers that small, however, saturate rather easily, especially at low frequencies. They restrict the maximum output voltage and thus the maximum SPL of the microphone. More modern condenser microphones generally add an active output stage which is direct coupled, i.e. transformerless. That arrangement requires substantially more operating current, but also offers much better headroom, and greatly improves the ability to drive long cable runs.

 

The DC converter that John mentioned improves the sensitivity of the microphone, since all other things being equal, the sensitivity is proportional to the capsule's polarization voltage, and those converters typically put out around 60 Volts. They're also almost a necessity in a modern 48-Volt microphone, since the increased current draw of the output stage causes a larger voltage drop across the 6.8 kOhm resistor pair in the phantom supply. Thus a microphone that draws 4 mA, for example (2 mA per resistor -> 13.6 V drop across 6.8 kOhms), actually receives a voltage in the low-to-middle 30s rather than 48. It would cause a major step backwards in sensitivity if such a low voltage were used to polarize the capsule.

 

So: The original, analog version of the Neumann KMR 81 is one of the last remaining holdovers from their fet 80 series, which began with the KM 84 microphone in 1966. It features the older, simpler, lower-current, transformer-output type of circuit, with lower headroom (as a wild guess, maybe 6 to 10 dB lower) than it could have with more modern circuitry. It still does well for its age, though--it can put out about 900 mV (when lightly loaded) if it has to, for a maximum SPL of 128 dB (again, when lightly loaded).

 

It's a nice-sounding microphone in my opinion. I don't know how well it does in high humidity, though; it's a traditional DC-polarized condenser, and for situations with any risk of moisture condensation, RF condenser microphones are generally considered more reliable.

 

--best regards

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